Stepping mechanism for use in a pinball machine or the like



June 25, 1968 R. F. GARBARK 3,390,255

STEPPING MECHANISM FOR USE IN A PINBALL MACHINE OR THE LIKE I5Sheets-Sheet 1 Filed Aug. 9, 1965 EMVEMTOR) ROMAN F. GARBARK 4?CATTor-zmsy/ Jun 25, 1968 R- F. GARBARK STEPPING MECHANISM FOR USE IN APINBALL MACHINE OR THE LIKE 3 Sheets-Sheet 2 Filed Aug. 9, 19 5 VEMTQROMAN F, GARB 3 6:1:W6%7W, GM

(:flfl'cmsyw June 25, 1968 GARBARK 3,390,255

STEPPING MECHANISM FOR USE IN A PINBALL MACHINE OR THE LIKE 3Sheets-Sheet 5 Filed Aug. 9, 1965 ROMAN F. GARBARK United States Patent3,390,255 STEPPING MECHANISM FOR USE IN A PINBALL MACHINE OR THE LIKERoman F. Gal-bark, Westchester, Ill., assignor to D.

Gottlieb & Co., Chicago, Ill., a corporation of Illinois Filed Aug. 9,1965, Ser. No. 478,256 14 Claims. (Cl. 235-92) The present inventionrelates to stepping mechanisms and more particularly to an improvedcounter mechanism of the drum type suitable for tallying the score in acoinoperated amusement device.

It is an object of the present invention to provide a stepping mechanismwhich is faster and more reliable and efficient than prior devices usedfor this purpose. More specifically it is an object to provide astepping mechanism which is capable of accurate stepping with only smallamounts of input power, which has low inherent friction and in whichinertial forces are reduced to a minimum. It is a related object toprovide a stepping mechanism which is durable and capable of consistentoperation over many thousands of counting cycles.

It is another object of the present invention to provide a steppingmechanism which consists of a minimum of simply formed parts and whichhas a high degree of compactness enabling similar units to be assembledside by side in compact relation, one unit for each decimal orderdesired.

It is a further object of the invention to provide a stepping mechanismwhich is inherently inexpensive making use of low cost parts which servemultiple purposes, which is easily assembled and easily serviced.

It is still another object of the invention to provide a novel steppingmechanism which includes a printed circuit switch board as an integralpart of the construction producing a high degree of reliability ofcontact with a minimum of loading upon the drive mechanism. In short itis an object of the present invention to provide a stepping mechanismwhich is reliable and which is capable of operating for long periodswithout special lubrication, cleaning or other maintenance.

Other objects and advantages of the invention will become apparent uponreading the attached detailed description and upon reference to thedrawings in which:

FIGURE 1 is a diagrammatic perspective showing a pinball machine of thetype employing the present invention.

FIG. 2 is a perspective view of a counting assembly employing several ofthe stepping mechanisms.

FIG. 3 is a vertical section taken along the line 33 through one of thestepping mechanisms of FIG. 2 in the deenergized condition.

FIG. 4 is a horizontal section taken along the line 4-4 in FIG. 3.

FIG. 5 is an exploded perspective illustrating the ratchet drivingelements. Y

FIG. 6 is a fragmentary section taken through the ratchet drivingelements along the line 66 in FIG. 3.

FIG. 7 is a perspective showing the inside surface of the printedcircuit assembly.

FIG. 8 is a fragmentary exploded perspective showing the contacts on thecircuit board.

FIG. 9 is a fragmentary perspective showing the wiper assembly.

FIG. 10 is a vertical section similar to FIG. 3 but with certain partsomitted and showing the device in its energized condition.

FIG. 11 is a fragmentary elevation of the switch contact assembly.

FIG. 12 is a fragmentary section taken along the line 3,390,255 PatentedJune 25, 1968 "ice 12-12 in FIG. 3 showing the mode of securingindividual stepping mechanisms in the supporting channels.

While the invention has been described in connection with the preferredembodiment, it will be understood that it is not intended to be limitedto the particular embodimen shown but it is intended to cover thevarious alternative and equivalent constructions included within thespirit and scope of the appended claims.

Turning now to FIGURES 1 and 2 there is shown an amusement device in theform of a pinball machine 20 having a play field 21, a plunger 22, acoin receiver 23, and a console 24 which may have one or more countingassemblies 25 for the purpose of tallying the score.

A typical counting unit 25 has three stepping mechanisms which areidentical to one another, and in the discussion which follows emphasiswill be placed upon the distinguishing features and advantages of theimproved mechanism. As is conventional in counter practice, anelectrical impulse fed to the unit in the lowest decimal order causesthat unit to index forwardly one step, and upon completion of arevolution a carry impulse is transmitted from the unit of lowest orderto the unit in the next higher order. Such unit, in turn, produces acarry impulse which is transmitted to the unit of still higher order, sothat the size of the number which can be totaled and displayed islimited only by the number of stepping units used. Switching means isnormally provider for restoring the counter to zero count at the end ofplay. Since the electrical wiring for the counting and restoringfunctions is conventional, it need not be described.

The stepping mechanism, or stepping unit, shown in FIG. 3 and in thesucceeding figures includes a frame plate 31, which may be of steel andwhich forms one of the side walls of the unit. The plate is preferablybent at 32 to form an end wall 33 and bent again to form a mountingflange 34 (see especially FIG. 4). Projecting at right angles from thecenter of the plate 31 is a stub shaft 35 having its base spun orriveted in place as shown at 36 and having a groove 37 formed on its tipfor receiving a snap washer as will be described.

Telescoped over the shaft 35 is a rotatable indicator drum 40 having acentral hub 41 and web 42 including a set of spokes 43 terminating in anouter shell 44. As shown, the shell is preferably formed of ten fiattedareas carrying the numerals 1-9 and 0. The web 42 is recessed to define,with the shell, what may be termed a drum hollow 45.

Turning next to the driving means for the drum, a rack plunger isprovided of generally flat configuration inter posed between the frameplate 31 and the drum hollow 45. The plunger has lateral edges 51, 52which are parallel to one another and which are received forreciprocating movement in guide members 53, 54, the latter beingintegral with the frame plate and arranged generally opposite oneanother, adjacent the outer end 55 of the plunger. At its inner ordriven end 56 the plunger is transversely bent to form a yoke having aU-shaped notch 57. Buttons 58 reduce friction.

To drive the plunger a solenoid 60 is provided having a coil 61 and acentral core or armature 62, the outer end of which is formed with ahead 63 which is captively received in the slot 57. It is one of thefeatures of the solenoid 60, as brought out in FIGS. 4 and 5, that theframe plate 31, and the end portion 33 which is integral with it, formsa portion of the external magnetic circuit of the solenoid. The circuitis efficiently completed by a generally L-shaped pole piece 65, made ofsteel stock, consisting of a first portion 66 which extends along oneside to the coil and a second portion 67 which is bent around the faceof the coil carrying mounting pads 68 which are secured, by suitablemachine screws, to the inside surface of the frame plate. It is one ofthe features of the design that the mounting pads 68 are spaced from oneanother so as to guidingly embrace the inner end of the rack plunger 50.The guidance provided by the guides 53, 54 plus that provided by thepads 68 insures that the plunger undergoes pure reciprocation.

For the purpose of restoring the rack plunger 50 to an initial positionwhen the solenoid is deenergized, and thereby providing the drivingforce for the drum, a rack drive spring 70 is arranged parallel to therack plunger, with one end secured to an integral ear or hook 71 on theplunger and the other end anchored to the frame plate via the guidemember 53.

In carrying out the present invention the reciprocating movement of theplunger is converted to rotary step-bystep movement by means of a rotarydrive pawl, or drive spool, 80 of cylindrical shape having axiallyfacing pawl teeth at its inner end. The drive pawl i arranged coaxiallyin the drum and extends sideways from the rack member into the drumhollow for engagement with cooperating surfaces formed on the web 42 ofthe drum. The rotary pawl member 80 is caused to oscillate by arack-andpinion connection with the plunger. A rack, indicated at 81, isformed along one side of a central window opening 82 in the plunger. Thecooperating pinion, or gear, 83 is formed integrally at the outer end ofthe pawl member and, since a relatively short pawl stroke suflices, thetoothed segment is partial rather than being complete. The pawl memberis preferably made of nylon or equivalent, the plunger of stainlesssteel.

For advancing the drum 40 incident to oscillation of the pawl member, aset of ratchet teeth 85 are provided on the web 42 of the drum facingaxially and spaced closely adjacent the drum hub 41 to cooperate withthe set of pawl teeth, indicated at 86, formed on the inner end of thepawl member. For the purpose of biasing the pawl member relative to thedrum, the pawl member has a cylindrical hollow 87 (see FIG. 6) definingan internal annular seat or shoulder 88 for seating a coil spring 89.The base of the spring is supported on an annular embossment 90 whichserves as a guide, or hearing, for the outer end of the pawl member. Inorder to prevent retrograde movement of the drum, a set of index teeth92 are provided on the drum web 42 but at a greater radius than theratchet teeth 85. An index pawl, or keeper pawl, 93 is provided in theform of a thin cantilever spring having a tip 94 and a base which isadjustably anchored to the frame by a pair of machine screws 95. A slot96 formed in the base permits endwise adjustment for accuratepositioning with respect to the index teeth.

In accordance with one of the more detailed features of theconstruction, the rack drive spring 70, and its attaching hook 71 on theplunger are located off of the center line of the plunger in such aposition as to produce, in addition to the driving force, a smallamount-of rotational torque in the plane of the plunger in such adirection as to urge the rack 81 resiliently into engagement with theteeth of the pinion 83, thus taking up any lost motion at the region ofengagement and compensating for any wear which may occur at the teeth.In analyzing this effect, the stationary guide 53 at the outer end ofthe plunger may be considered as the fulcrum. Suflicient play isprovided between the pads 68 and the inner end of the plunger to insurethat take-up movement will occur at the rack teeth.

In a typical operating sequence, the solenoid 60 is energized, suckingin the solenoid core 62 and causing movement of the plunger to the rightas viewed in FIGS. 3, 4 and 5. The stationary index pawl 93, engagingone of the index teeth 92, holds the drum in position so that one stepof idle clicking takes place between the ratchet teeth 85 and the pawlteeth 86 on the rotary pawl member. Elongation of the rack drive spring70 serves to store the energy used for driving purposes. At thetermination of the solenoid input pulse, the plunger is released by thesolenoid for leftward movement under the urging of the rack drivespring, accompanied by rotation of the rotary pawl member which istranslated, via the ratchet and pawl teeth, 85, 86, into a step offorward movement, or indexing, of the drum. During such forward movementan idle click occurs at the index pawl 93.

For the purpose of blocking the drum in a precisely indexed position, adog is provided on the rack plunger which cooperates with a series ofreinforcing ribs formed on the inside of the drum. Thus there isprovided on the outer end of the plunger a dog 100 in the form of anintegral, bentover tab, which is in the normal path of movement of aseries of reinforcing ribs 101. As will be apparent from FIG. 5, thereinforcing ribs are of triangular shape, anchored along one edge to therespective spokes '43 in the drum and, along an adjacent edge, to the.drum shell 43. When the'solenoid is energized, the dog 100 is, ofcourse, retracted. Thus when the solenoid is subsequently released thedrum is free to begin a step of rotation under the urging of the drivespring 70. However, as the plunger approaches its normal, outwardlyextended limit position, the dog 100 is interposed in the path ofmovement of the approaching one of the reinforcing ribs 101, therebystopping the drum in a precise, registered position. In this connectionit may be noted that no special stop need be provided for limiting theoutward movement of the plunger. The stop function is performed byengagement between the edge 82a of the window 82 in the plunger with thesmooth surface 83a adjacent the toothed segment 83 on the rotary pawlmember.

It is one of the features of the present construction that the drum 40may be formed of a single molded piece of plastic in extremely lightcross section resulting in a minimum of inertia so that extremely rapidindexing may occur with only a small amount of energy from the rackdrive spring 70. In order to further reduce the energy requirement, theratchet teeth 85, pawl teeth 86, and index teeth 92 are made extremelyshallow so that only small amounts of energy need be expended in flexingthe pawl biasing spring 89 and the leaf spring which forms the indexpawl 93. In order to maintain a high degree of reliability with ashallow tooth height, and to preclude any possibility that deformationmight take place in the web portion 42 of the drum due to its thinsection combined with the dimensional changes which may occur in plasticmaterials, for example as a result of age, a camming ridge reinforcementis provided between the ratchet teeth 85 and index teeth 92. The ridgenot only insures against web deformation but serves as a cam surface tooperate a cam follower coupled to a switch operating member forswitching purposes. Thus, referring to FIGS. 5 and 6, a thin,cylindrical camming ridge is provided on the drum. Such ridge, in spiteof its narrow radial dimension, has a substantial web-stiffening effect.

Cooperating with the cam is a switch operator 111 (see FIGS. 10 and 11)in the form of a bent piece of wire having a cranked cam follower 112and a switch arm 113. The latter controls a switch 115 formed of aseries of stacked switch blades. For seating the switch operator 111 andfor establishing a normal position for the operator, a switch leverspring 116 is provided. The latter is hooked ontoa cranked offset 117 ofsmall radius in a direction to keep the operator seated in notchesformed in a pair of supports 118, 119 integral with the frame plates. Itwill be apparent that the spring serves to fcenter the switch operatorin a precise position without reliance upon any stops whatsoever.Moreover it may be also noted that a relatively stiff spring 116 may beused, thereby keeping the switch operator seated in spite of shock andvibration, without, however, imposing any great amount of torqueloading. Indeed, the amount of loading, or restoring effect, may betailored to any desired amount simply by changing the radius of theoffset 117. The net result is that positive actuation of the switch 115may be achieved with only limited torque requirements at the cam 110 andconsequently with only negligible loading of the rack drive spring 70.

In accordance with one of the aspects of the present invention, acircuit board is utilized as the opposite side wall of the steppingmechanism arranged parallel to the frame plate 31. Thus referring toFIGS. 7 and 8, a printed circuit board 130 is used having mounting legs131, 132 which are secured to the flange 34 of the frame plate and whichdefine a central clearance space 133 which clears the solenoid polepiece 66. The opening .135 in the board receives the tip of the stubshaft 35. For commutation as the drum is indexed from one position tothe next, segmented contacts, ten in number, are provided equally spacedabout the shaft and connected to respective terminals 136 convenientlyprovided at the edge of the circuit board. In order to avoid necessityfor using a pigtail, a concentric ground plate 137, isolated by anaccompanying insulator 138, is riveted to the board. The ground terminalis brought out to terminals 139 at the respective edges of the circuitboard.

For contacting the contact segments and ground plate, a resilient wiperassembly 140 is provided in the form of a thin sheet of Phosphor Bronzehaving a first wiper arm 141 and second wiper arm 142. The wiperassembly, in the present instance, is rigidly coupled to the hub of thedrum by making the end of the hub of castellated shape as shown at 145fitted into a correspondingly shaped opening 146 in the body portion ofthe wiper. The end 145 of the hub is received in a thrust bearing 147formed of plastic or the like. Such thrust bearing, pressing against theland surrounding the opening .135 in the circuit board, serves tomaintain the drum in a fixed axial position, notwithstanding the thrustof the pawl biasing spring 89. A spring retaining clip 148, fitted intothe groove 37 at the end of the shaft, together with an accompanyingspring washer 149 serve to complete the assembly. Since the spacingbetween the wiper assembly and the circuit board is maintained constantdepending upon the thickness of the thrust bear-ing 147, the wiper arms141, 142 may be precisely adjusted to provide adequate contact with thecontact sectors and ground plate but with a minimum loading upon thedrive spring 70.

The net result of the above construction is to produce a steppingmechanism which fulfills all of the objects originally set forth. Only asmall amount of energy is required to produce rapid, positive action.Lubrication and other operating parameters are noncritical; thusmaintenance is reduced to a minimum. When maintenance of the contacts isrequired, it is a simple matter, involving the removal of only twoscrews and a spring clip to expose the contacts on the circuit board forinspection or cleaning.

While the present invention has to do primarily with the construction ofthe individual stepping mechanisms, mention may also be made of themanner in which such stepping mechanisms are integrated in a typicalcounting unit. Thus, referring again to FIG. 2, the counting unit 25 hasa top plate 151 and bottom plate 152 which are equipped, at their ends,with mounting brackets 153. The top and bottom plates, which may beconstructed either identically or as mirror images of one another, carryaligned channels 155, formed of soft slippery plastic, for example,polyethylene, which may be riveted or otherwise secured in place forcushioned channeling the presented upper and lower edges of therespective stepping units, free of any supporting contact with thecircuit boards. Each unit may be locked in position by providingregistering holes in the frame plates and channel members respectivelyengaged by a suitable spring clip, for example, a clip. having the shapeindicated at 160 in FIG. 12. Illumination is provided by lamps 165mounted in suitable sockets provided in a lamp strip member 166, securedto the respective top and bottom plates by soft rubber grommets 167engaging registering openings. The

plastic channels serve to mufile the vibration which is incident tonormal operation, and the grommet mounting provides further protection,against vibration, for the lamps 165.

I claim as my invention:

1. In a stepping mechanism for use in a pinball machine or the like, thecombination comprising a frame plate mounting a shaft, an indicator drumhaving a hub journaled on the shaft and having a central web recessed todefine a drum hollow, a flat rack member arranged adjacent the drumhollow, means including a solenoid and return spring for reciprocatingthe rack member, a rotary pawl member extending axially into the drumhollow, a first set of axially facing ratchet teeth on the web adjacentthe hub, a set of pawl teeth on the pawl member for cooperating with thefirst set of ratchet teeth, means for biasing the pawl member endwise, asecond set of axially facing ratchet teeth surrounding said first set, akeeper pawl secured with respect to the frame plate for cooperating withthe teeth of the second set, and a rack and pinion connection betweenthe rack member and the pawl member so that when the rack member isreciprocated by the solenoid the rotary pawl member oscillates forindexing of the drum through one step of movement.

2. In a stepping mechanism for use in a pinball machine or the like, thecombination comprising a frame plate having a stub shaft, an indicatordrum arranged parallel to the frame plate having a hub journaled on theshaft and a central web recessed to define a drum hollow, a flat rackmember interposed between the frame plate and the drum hollow, meansincluding a solenoid and return spring for reciprocating the rackmember, a set of axially facing ratchet teeth on the web surrounding thehub, a rotary pawl member of hollow cylindrical construction journaledon the hub and extending from the rack memher into the drum hollow, saidpawl member having a set of pawl teeth on the inner end thereof forcooperating with the set of ratchet teeth and having an internal annularshoulder, a coil spring in the pawl member seated on the shoulder forpressing the pawl member toward the ratchet teeth, a rack on the rackmember, gear teeth on the outer end of the pawl member so that uponsuccessive actuations of the solenoid the drum is indexed forwardly stepby step.

3. In a stepping mechanism for use in a pinball machine or the like, thecombination comprising a frame plate mounting a shaft, an indicator drumhaving a hub ournaled on the shaft and having a central web defining adrum hollow, a flat rack member arranged adjacent the drum hollow, meansincluding a solenoid and return spring on the frame plate forreciprocating'the rack member, a rotary pawl member extending axiallyfrom the rack member into the drum hollow, a set of axially facingratchet teeth on the web, a set of cooperating pawl teeth on the pawlmember, means for biasing the pawl member toward the web, and a rack andpinion connection between the rack member and the 'pawl memher foroscillating the pawl member.

4. In a stepping mechanism for use in a pinball machine or the like, thecombination comprising a frame plate mounting a shaft, an indicator drumhaving a hub ournaled on the shaft and having a central web which isrecessed in the drum to define a drum hollow, a rack member arrangedflatly adjacent the drum hollow, means including a solenoid and returnspring for reciprocating the rack member, a rotary pawl member extendingaxially from the rack member into the drum hollow, first and second setsof axially facing ratchet teeth on the web, a set of pawl teeth on theinner end of the pawl'member for cooperating with the first set ofratchet teeth, a keeper pawl on the frame plate for cooperating with thesecond set of ratchet teeth to prevent retrograde movement of the drum,a rack and pinion connection between the rack member and the rotary pawlfor extending the drum forwardly upon successive energizations of thesolenoid, a switch mechanism having an operator, the drum including theweb portion thereof being formed of plastic in thin light cross section,and a cylindrical camming ridge integral with the web between the firstand second sets of ratchet teeth for cammingly engaging the switchoperator and for providing reinforcement of the web so that the ratchetteeth are maintained accurately in position notwithstanding dimensionalchanges in the plastic.

5. In a stepping mechanism for use in pinball machine or the like, thecombination comprising a frame plate mounting a shaft, an indicator drumhaving an outer cylindrical shell and a hub journaled on the shaft aswell as a central web recessed to define a drum hollow, a rack memberarranged flatly adjacent the drum hollow, means including a solenoid andreturn spring for reciprocating the rack member, a rotary pawl memberextending axially from the rack member into the drum hollow, a set ofaxially facing ratchet teeth on the web adjacent the hub, a set ofcooperating pawl teeth at the inner end of the pawl member, means forbiasing the pawl member endwise for engagement of the teeth, a rack andpinion connection between the rack member and the pawl member so thatsuccessive actuations of the solenoid cause the drum to be indexinglyadvanced, said drum having reinforcing ribs extending radially inwardfrom the shell into the drum hollow, and a dog on the rack member sopositioned as to be interposed in the path of movement of the ribs whenthe solenoid is deenergized for positively blocking the drum and forholding the same in indexed position.

6. In a stepping mechanism for use in pinball machine or the like, thecombination comprising a frame plate mounting a shaft, an indicator drumhaving an outer cylindrical shell and a central web recessed to define adrum hollow, a rack member in the form of a generally flat stripinterposed between the frame plate and the drum hollow, a rotary pawlmember of generally cylindrical shape extending from the rack memberinto the drum hollow, said web having a set of axially facing ratchetteeth and said pawl member having a cooperating set of axially facingpawl teeth, means for biasing the pawl member with respect to the drumto maintain the teeth in engagement, rack teeth formed on the rackmember, gear teeth formed on at least a segment of the pawl member formeshing therewith, a solenoid coupled to one end of the rack member,guiding means at the other end of the rack member so that the rackmember moves in a straight line when the solenoid is energized, a rackdrive spring interconnected between the frame and the rack member forproducing return movement of the rack memher when the solenoid isdeenergized, the rack drive spring being connected to the rack so as toprovide a component of force in a direction to maintain engagement freeof play between the rack teeth and the gear teeth.

7. In a stepping mechanism for use in a pinball machine or the like, thecombination comprising a frame plate mounting a shaft, an indicator drumon the shaft having an outer cylindrical shell and a central web whichis recessed therein to define a drum hollow, a rack member arrangedflatly adjacent the drum hollow, a rotary pawl member of generallycylindrical shape extending axially from the rack member into the drumhollow, a set of axially facing ratchet teeth on the web and a set ofcooperating pawl teeth on the inner end of the pawl member, means forbiasing the pawl member with respect to the drum to maintain the teethin contact, a central opening in the rack member for accommodating theouter end of the pawl member, the rack member having a rack on one sideof the opening and the pawl member having teeth for meshing therewith, asolenoid coupled to one end of the rack member, guiding means forengaging the other end of the rack member for guiding the same forreciprocating movement, a rack drive spring arranged along the edge ofthe rack member which is opposite the rack and connected to the rackmember at a point intermediate the solenoid and guiding means so thatthe spring serves not only to return the rack member when the solenoidis deenergized but to apply a component of force to the rack member tomaintain the rack member mesh with the teeth on the pawl member.

8. In a stepping mechanism for use with a pinball machine or the like,the combination comprising a frame plate mounting a shaft, an indicatordrum journaled on the shaft and having an outer cylindrical shell andcentral web defining a drum hollow, a rack member arranged flatlyadjacent the drum hollow, means including a solenoid connected to oneend of the rack member together with a return spring for reciprocatingthe same, a rotary pawl member of generally cylindrical shape extendingaxially into the drum hollow, a set of ratchet teeth on the web and aset of cooperating pawl teeth on the inner end of the pawl member, arack and pinion connection between the rack member and the pawl member,a switch mechanism, a switch operator for the switch mechanism, acylindrical camming ridge on the web surrounding the ratchet teeth, saidswitch operator being in the form of a length of wire rockably supportedon the frame plate and having one end bent to form a cam follower crankfor riding on the camming ridge so that the switch is actuated at apredetermined phase position of the drum.

9. In a stepping mechanism for use with a pinball machine or the like,the combination comprising a frame plate mounting a shaft, an indicatordrum journaled on the shaft and having an outer cylindrical shell andcentral web defining a drum hollow, a rack member arranged flatlyadjacent the drum hollow, means including a solenoid connected to oneend of the rack member together with a return spring for reciprocatingthe same, a rotary pawl member of generally cylindrical shape extendingaxially into the drum hollow, a set of ratchet teeth on the web and aset of cooperating pawl teeth on the inner end of the pawl member, arack and pinion connection between the rack member and the pawl member,a switch mechanism, a switch operator for the switch mechanism, .acylindrical camming ridge on the web surrounding the ratchet teeth, saidswitch operator being in the form of a length of wire rockably supportedon the frame plate and having one end bent to form a cam follower crankfor riding on the camming ridge so that the switch is actuated at apredetermined phase position of the drum, the switch operator having acranked offset of short radius at the central portion thereof and havinga tension spring connected thereto tending to resiliently center thespring operator for maintaining the cam follower crank in engagementwith the camming ridge.

10. In a stepping mechanism for use in .a pinball machine or the like,the combination comprising a frame plate mounting a stub shaft at rightangles thereto and forming the side wall of an enclosure, said platehaving a laterally bent portion forming the end Wall of the enclosureand defining a mounting flange, an indicator drum journaled on the shaftand having an outer cylindrical shell as well as a central web recessedto define a drum hollow, a flat rack member arranged adjacent the drumhollow, a solenoid at said end wall coupled to one end of the rackmember, a return spring connected to the rack member, a rotary pawlmember extending axially from the rack member into the drum hollow, aset of axially facing ratchet teeth on the web and a set of cooperatingpawl teeth on the inner end of the pawl members, means for biasing thepawl member endwise for maintaining the teeth in axial engagement, arack and pinion connection between the rack member and the pawl member,a printed circuit board arranged parallel to the frame plate to definean opposite side wall and secured to said mounting flange, contactsectors on said printed board, and a resilient wiper arm secured to thedrum for contacting the sectors in succession as the drum is indexed bythe solenoid.

11. In a stepping mechanism for use in a pinball machine or the like,the combination comprising a frame plate of magnetic material defining aside wall and having a bent over portion defining an end wall, anindicator drum having a hub journaled on the shaft and having a centralweb defining a drum hollow, a rack member arranged flatly along theframe plate adjacent the drum hollow, a solenoid having a coil andplunger, said plunger being coupled to the rack member, a return springconnected to the rack member, a rotary pawl member extending axiallyfrom the rack member into the drum hollow, a set of axially facingratchet teeth on the web, a set of cooperating pawl teeth on the pawlmember, and a rack and pinion connection between the rack member and thepawl member for oscillating the pawl member, said solenoid coil beingmounted closely adjacent the end wall and side wall so that the frameplate forms a magnetic circuit for the solenoid.

12. In a stepping mechanism for use with a pinball machine or the like,the combination comprising a plurality of vertical frame plates spacedside by side and having aligned stub shafts thereon, indicator drums onthe stub shafts, each of said indicator drums having an outercylindrical shell carrying indicia and a central web recessed to definea drum hollow, each of said drums having a rack member arranged flatlyadjacent the drum hollow, reciprocating means including solenoids andassociated return springs for reciprocating the rack members, each ofsaid drums having a rotary pawl member located in the drum hollow havinga ratchet connection at one end with the respective drum and having rackand pinion connection at the other end with the adjacent rack member,upper and lower horizontal mounting plates arranged parallel to oneanother, said mounting plates having channel members mounted thereon inrespective vertical alignment, the frame plates being dimensioned forsliding reception into aligned ones of said channel members for displayof indicia on the drums.

13. In a stepping mechanism for use with a pinball machine or the likethe combination comprising a plurality of stepping mechanisms eachhaving a rectangular frame plate and a circuit board in spaced parallelrelation, said frame plates having aligned stub shafts thereon,indicator drums on the stub shafts, each of said indicator drums havingan outer cylindrical shell carrying indicia and a central web recessedto define a drum hollow, each of said drums having a rack memberarranged flatly adjacent the drum hollow, reciprocating means includingsolenoids and associated return springs for reciprocating the rackmembers, each of said drums having a rotary pawl member located in thedrum hollow having a ratchet connection at one end with the respectivedrum and having rack and pinion connection at the other end with theadjacent rack member, upper and lower horizontal mounting platesarranged parallel to one another, said mounting plates having channelmembers of soft plastic material mounted thereon in respective verticalalignment, the frame plates being dimensioned for sliding receptionbetween aligned ones of said channel members with the circuit boardsfree of any supporting contact with the mounting plates.

14. In a stepping mechanism for use in a pinball machine or the like thecombination comprising a frame plate mounting a shaft at right anglesthereto, an indicator drum journaled on the shaft having an outercylindrical shell and a central web recessed to define a drum hollow, arack member arranged flatly adjacent the drum hollow, means including asolenoid and return spring for reciprocating the rack member, a rotarypawl member extending axially from the rack member into the drum hollow,a set of axially facing ratchet teeth on the web and a set ofcooperating pawl teeth on the pawl member, a rack and pinion connectionbetween the rack member and the pawl member, a circuit board on theopposite side of the drum from the frame plate and secured to the latterin parallel relation, contacts in a circular locus on the circuit board,a resilient wiper arm secured to the drum for wiping the contacts, athrust bearing interposed between the wiper arm and the circuit board,and a biasing spring in the rotary pawl member for urging the pawlmember into axial engagement with the drum and for urging the drum intobottoming engagement with respect to the circuit board thereby tomaintain an accurate spacial relationship between the wiper arm and thecontacts on the circuit board.

References Cited UNITED STATES PATENTS 2,193,629 3/1940 Hopping 235-922,883,194 4/1959 Bogner 235-92 3,341,694 9/1967 Heimberger 235-92MAYNARD R. WILBUR, Primary Examiner.

G. J. MAIER, Assistant Examiner.

1. IN A STEPPING MECHANISM FOR USE IN A PINBALL MACHINE OR THE LIKE, THECOMBINATION COMPRISING A FRAME PLATE MOUNTING A SHAFT, AN INDICATOR DRUMHAVING A HUB JOURNALED ON THE SHAFT AND HAVING A CENTRAL WEB RECESSED TODEFINE A DRUM HOLLOW, A FLAT RACK MEMBER ARRANGED ADJACENT THE DRUMHOLLOW, MEANS INCLUDING A SOLENOID AND RETURN SPRING FOR RECIPROCATINGTHE RACK MEMBER, A ROTARY PAWL MEMBER EXTENDING AXIALLY INTO THE DRUMHOLLOW, A FIRST SET OF AXIALLY FACING RATCHET TEETH ON THE WEB ADJACENTTHE HUB, A SET OF PAWL TEETH ON THE PAWL MEMBER FOR COOPERATING WITH THEFIRST SET OF RATCHET TEETH, MEANS FOR BIASING THE PAWL MEMBER ENDWISE, ASECOND SET OF AXIALLY FACING RATCHET TEETH SURROUNDING SAID FIRST SET, AKEEPER PAWL SECURED WITH RESPECT TO THE FRAME PLATE FOR COOPERATING WITHTHE TEETH OF THE SECOND SET, AND A RACK AND PINION CONNECTION BETWEENTHE RACK MEMBER AND THE PAWL MEMBER SO THAT WHEN THE RACK MEMBER ISRECIPROCATED BY THE SOLENOID THE ROTARY PAWL MEMBER OSCILLATES FORINDEXING OF THE DRUM THROUGH ONE STEP OF MOVEMENT.